The present invention relates generally to hydraulic systems for supplying fluid to a plurality of fluid operated devices and more particularly to a hydraulic liquid reservoir from which hydraulic fluid is withdrawn through a pump and delivered to a fluid operated device and then is returned to the reservoir.
Many vehicles and implements now utilize a hydraulic system as the major power source for operating any number of devices associated with the vehicle. For example, in industrial earthworking equipment, a plurality of fluid rams are utilized for manipulating various components of various earthworking implements and the fluid rams are supplied with pressurized fluid through a pump that withdraws fluid from a reservoir. In order to simplify the hydraulic control circuit in many of the smaller units, such units employ what is commonly termed an open-center system wherein the valves that control the fluid to and from the various fluid rams allow the pressurized fluid to pass through the associated valve when the valve is in a neutral condition which is then returned to the reservoir.
With this type of hydraulic system, it is customary to utilize a constant flow pump and have all of the output of the pump bypass either through the valve or through a bypass system and returned to the reservoir when none of the fluid rams associated therewith are being actuated. Also, in order to provide a system at reduced cost, normally a single pump supplies pressurized fluid to a plurality of valves which are respectively connected to a plurality of fluid rams. Thus, when any of the valves are moved to an operative position, pressurized fluid is delivered to the associated fluid ram. Under these circumstances, it is necessary for the pump to have a substantially high capacity of hydraulic liquid in order to supply all of the fluid rams simultaneously, should such a need arise.
With such high output pumps, difficulties have been encountered in creating turbulence within the reservoir as the hydraulic fluid or liquid is being returned to the reservoir either directly from the pump or after it has been diverted through the respective fluid rams. This turbulent condition results in creating air bubbles in the hydraulic liquid or oil within the reservoir which are difficult to remove and result in reducing the output of the pump and can also result in cavitation of the pump should the aeration become excessive.
Various proposals have been made for reducing the aeration of the hydraulic oil within the reservoir and one such proposal consists of a baffle located between the reservoir inlet and the reservoir outlet. Other proposals have been suggested such as disclosed in U.S. Pat. No. 3,002,355, which proposes a substantially closed passage between the inlet pipe of the tank and the outlet. However, such a proposed system has inherent shortcomings in that the dwell time of the hydraulic liquid that is being returned to the reservoir is at a minimum because it is substantially entrapped under the member that defines the passage which prevents mixture of the return oil with the remaining oil for cooling purposes.